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SYSTEMATIC NAME

IUBMB Comments

1,5-anhydro-D-fructose hydro-lyase (microthecin-forming)

This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose [1,2]. Aldose-2-uloses such as 2-dehydroglucose can also act as substrates, but more slowly [1,2,4]. This is a bifunctional enzyme that acts as both a lyase and as an isomerase [2]. Differs from EC 4.2.1.111, which can carry out only reaction (1a), is inhibited by its product and requires metal ions for activity [1].

removal of two zinc ions at the bottom of two putative active-site clefts in the propeller and the cupin domains leads to loss of enzymatic activity, although the structure of the Zn2+-depleted enzyme is very similar to that of native AUDH

the bifunctional enzyme aldos-2-ulose dehydratase/isomerase participates in carbohydrate secondary metabolism, catalyzing the conversion of glucosone and 1,5-D-anhydrofructose to the secondary metabolites cortalcerone and microthecin, respectively

dehydration reaction most likely follows an elimination mechanism, where Zn2+ acts as a Lewis acid polarizing the C2 oxo group of 1,5-D-anhydrofructose. The reaction intermediate ascopyrone M shows binding of this compound at two different sites, with direct coordination to Zn2+ in the propeller domain and as second sphere ligand of the metal ion in the cupin domain

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

formation of microthecin is irreversible. 1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose [1,2]. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

i.e. D-arabino-hexos-2-ulose. The enzyme dehydrates D-arabino-hexos-2-ulose, generating a double bond between C-3 and C-4. This unsaturated compound is proposed to be the steady-state intermediate characterized by the spectral peak at 265 nm. This intermediate is chemically unstable and rearranges from its strained 1,5 ring form to a more stable 2,6 pyranose structure. Then the enzyme acts a second time, dehydrating this pyranose structure to form cortalcerone

i.e. D-arabino-hexos-2-ulose. The enzyme dehydrates D-arabino-hexos-2-ulose, generating a double bond between C-3 and C-4. This unsaturated compound is proposed to be the steady-state intermediate characterized by the spectral peak at 265 nm. This intermediate is chemically unstable and rearranges from its strained 1,5 ring form to a more stable 2,6 pyranose structure. Then the enzyme acts a second time, dehydrating this pyranose structure to form cortalcerone

the product absorbs at 260 nm but no conversion into a 230 nm-absorbing product occurs. Because of its strained nature, the intermediate still rearranges, losing UV absorbance, but since it lacks the 6th carbon, it cannot form a 2,6-pyranose ring to generate a second substrate for the enzyme

the product absorbs at 260 nm but no conversion into a 230 nm-absorbing product occurs. Because of its strained nature, the intermediate still rearranges, losing UV absorbance, but since it lacks the 6th carbon, it cannot form a 2,6-pyranose ring to generate a second substrate for the enzyme

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

1,5-anhydro-D-fructose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one + H2O (overall reaction), (1a) 1,5-anhydro-D-fructose = 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose + H2O, (1b) 1,5-anhydro-4-deoxy-D-glycero-hex-3-en-2-ulose = 2-hydroxy-2-(hydroxymethyl)-2H-pyran-3(6H)-one. This enzyme catalyses two of the steps in the anhydrofructose pathway, which leads to the degradation of glycogen and starch via 1,5-anhydro-D-fructose [1,2]. The other enzymes involved in this pathway are EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase), EC 4.2.2.13 (exo-(1,4)-alpha-D-glucan lyase) and EC 5.3.3.15 (ascopyrone tautomerase). This is a bifunctional enzyme that acts as both a lyase and as an isomerase. Differs from EC 4.2.1.111, which can carry out only reaction 1a

the enzyme contains a structural Zn2+ located in loop regions and two zinc ions at the bottom of two putative active-site clefts in the propeller and the cupin domain, respectively. Catalysis is dependent on these two zinc ions, as their specific removal leads to loss of enzymatic activity, metal binding site and structure, overview

at a pH lower than 5.0, the reaction rate is slower and there is a tendency for increased formation of degradation products (FHMK), at a pH higher than 5.5, there is a tendency for more APT dihydrate formation

at a pH lower than 5.0, the reaction rate is slower and there is a tendency for increased formation of degradation products (FHMK), at a pH higher than 5.5, there is a tendency for more APT dihydrate formation

Enzymatic description of the anhydrofructose pathway of glycogen degradation II. Gene identification and characterization of the reactions catalyzed by aldos-2-ulose dehydratase that converts 1,5-anhydro-D-fructose to microthecin with ascopyrone M as the intermediate